Packaging composition

ABSTRACT

The present invention relates to an improved packaging composition comprising an ethylene copolymer selected from ethylene acid or ester copolymers such as ethylene vinyl acetate, ethylene/acrylic acid or methacrylic acid copolymers which optionally contain a third comonomer such as an alkyl acrylate and the corresponding ionomers of said copolymers which are blended with a hydrophilic zeolite to form a composition which removes residual acids or small esters from the polymeric or ionomeric composition containing such residual acids. The acids may be present as initial by products in the copolymerization process or may be degradation products. The use of these compositions is particularly important when the resins are formed into packages or other fabricated material which are exposed to acid sensitive material.

This application claims the benefit of provisional application No.60/032,554 filed Dec. 12, 1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for removing residual acidsincluding acetic acid and acrylic or methacrylic acids from ethylenecopolymers such as ethylene vinyl acetate or ethylene acrylic acid orethylene methacrylic acid or ionomers thereof. The process is alsodirected to the removal of residual monomeric alkyl acrylates which maybe present in the ethylene copolymers.

2. Description of Related Art

Residual acids or monomeric alkyl acrylates formed during the productionprocess of ethylene copolymers have presented a continual technicalproblem, especially if the packaging material or wire and cable materialor other fabricated material is utilized to package or contain acid ormonomeric alkyl acrylate sensitive contents or material.

The use of a certain kind of zeolite to remove offensive odors orflavors is known. For example, WO 95/20624 published on Aug. 3, 1995describes the use of an adsorption agent which is added to films madefrom ethylene/acid copolymers to absorb odors. The siliceous materialdescribed therein is selected from those molecular sieves having aframework of tetrahedral oxide units, in which at least 90% of thetetrahedral oxide units are SiO tetrahedral, have a pore diametergreater than 5.5 Angstroms (preferably at least 6.0 Angstroms) and havea sorption capacity for water of less than 10% by weight at 25° C. and4.6 Torr (preferably less than 6% by weight). The preferred sieves arealso described as having a framework SiO₂/Al₂O₃ molar ratio of greaterthan 35, more preferably 200-500. This invention is also described inU.S. application Ser. No. 08/676,237. These molecular sieves are knownto be hydrophobic in that they sorb less than 10 wt. % water at 25° C.and 4.6 Torr pressure.

The present invention, on the other hand, is directed to the use of acompletely different molecular sieve for a particular purpose-thescavenging or removal or unwanted acid from ethylene copolymericmaterial which is utilized to contain or package acid or monomericacrylate sensitive material. The recited molecular sieves utilized inthis invention are hydrophilic in nature (e.g., absorb greater than 10%water at 25° C. and 4.6 Torr pressure) and are thus different than thatdescribed and used in the above patent publication.

BRIEF SUMMARY OF THE INVENTION

The present invention broadly relates to a process for removing unwantedacid or monomeric acrylate from an ethylene/acid copolymer comprising,

i) preparing a thermoplastic composition comprising an ethylene/acidcopolymer or ionomer thereof or an ethylene/acid/acrylate terpolymer orionomer thereof or an ethylene/vinyl acetate copolymer wherein thecomposition contains residual acid, and

ii) adding to the composition an acid scavenging agent selected from ahydrophilic molecular sieve which comprises a sodium aluminosilicatecontaining less than 5 wt. % of magnesium oxide and having asilica/alumina ratio of less than 100 and having a nominal pore diameterof 8-10 Angstroms. The preferred ratio is less than 35 and mostpreferred ratio is less than 3.0.

The invention further relates to a process as described above whereinthe molecular sieve preferentially absorbs acetic acid over water.

The present invention also relates to a method for packaging orcontaining an acid sensitive material comprising,

i) preparing a film or material comprising a thermoplastic compositioncomprising an ethylene/acid copolymer or ionomer thereof or anethylene/acid/acrylate terpolymer or ionomer thereof or anethylene/vinyl acetate copolymer and an acid scavenging agent selectedfrom a hydrophilic molecular sieve which comprises a sodiumaluminosilicate containing less than 5 wt. % of magnesium oxide andhaving a silica/alumina ratio of less than 100 (or less than 5 35 orless than 3.0) and having a nominal pore diameter of 8-10 Angstroms and

ii) packaging said film or material with the acid sensitive material.The material to be packaged, such as surgical sutures, can be packagedin such a way that the packaged material does not actually contact thepackaging surface but, the packaged material may still be exposed tofumes of acid which would come from the packaging material if thezeolite was not present.

The present invention also relates to a thermoplastic compositioncomprising an ethylene/acid copolymer or ionomer thereof or anethylene/acid/acrylate terpolymer or ionomer thereof or anethylene/vinyl acetate copolymer and an acid scavenging agent selectedfrom a hydrophilic molecular sieve which comprises a sodiumaluminosilicate containing less than 5 wt. % of magnesium oxide andhaving a silica/alumina ratio of less than 100 (or less than 35 or lessthan 3.0) and having a nominal pore diameter of 8-10 Angstroms. Theinvention also relates to a peelable seal composition comprising (a) azeolite concentrate which comprises an ethylene acid copolymer orionomer thereof and a hydrophilic molecular sieve which comprises asodium aluminosilicate containing less than 5 wt. % of magnesium oxideand having a silica/alumina ratio of less than 100 (or less than 35 orless than 3.0) and having a nominal pore diameter of 8-10 Angstroms and(b) a blend of (i) an ethylene acid copolymer or ionomer thereof and(ii) a polyolefin resin selected from a homopolymer or copolymer ofpolybutylene or blends of such polymers with polypropylene; or ahomopolymer or copolymer of polypropylene and further to this peelablecomposition coated onto an aluminum surface or a primed aluminum surfacewherein the primer is selected from a mixture of ethylene acid copolymeror ionomer thereof and the above zeolite. The invention further relatesto a composition as recited above wherein the molecular sievepreferentially absorbs acetic acid over water upon exposure of saidcomposition to an aqueous/acetic acid environment.

The present invention additionally relates to a multilayer packagingstructure comprising,

(a) an innermost layer comprising a thermoplastic ethylene copolymericcomposition comprising an ethylene copolymer and a zeolite selected froma molecular sieve which comprises a sodium aluminosilicate containingless than 5 wt. % of magnesium oxide and having a silica/alumina ratioof less than 100 (or less than 35 or less than 3.0) and having a nominalpore diameter of 8-10 Angstroms; and

(b) at least one additional polymeric, metallic or non-metallic layer.This additional polymeric layer may be selected from the same genericmaterial as the inner layer (a) (e.g. both layers do not have to be butmay be identical) or may be selected from a layer containing an ethylenecopolymeric packaging material which is, for example, an ethylene/acidcopolymer or ionomer containing film which does not have the molecularsieve contained therein or from a polyester or other common packagingmaterial. Such materials are sold under the trade names NUCREL®(ethylene acid copolymer) or SURLYN® (ethylene acid ionomer). Themetallic layer may be selected from a common packaging material such asaluminum. The multilayer structure can include additional layers asnecessary to form the desired package provided that at least one of thelayers is (a). The peelable seal composition described above can beextrusion coated onto a single layer or multilayer structure to form themultilayer structure containing said composition as a layer. Thepeelable seal composition can also be coextrusion coated onto analuminum surface of a multilayer aluminum substrate wherein a tie layerhaving a tie composition is the coextrusion component and actuallycontacts the surface of the aluminum. The tie layer can comprise anethylene acid copolymer/zeolite concentrate wherein the zeolite is type13X.

DETAILED DESCRIPTION

As summarized above, the present invention relates to a thermoplasticethylene copolymeric composition comprising an ethylene copolymer and azeolite selected from a molecular sieve which comprises a sodiumaluminosilicate containing less than 5 wt. % of magnesium oxide andhaving a silica/alumina ratio of less than 3.0 and having a nominal porediameter of 8-10 Angstroms. This composition is particularly useful inthe manufacture of articles which are ultimately destined to contain orpackage acid sensitive materials such as surgical sutures and the like.

The ethylene copolymers and terpolymers utilized herein are selectedfrom a wide variety of commercially available polymers which incorporateethylene as a basis monomeric unit and incorporate at least oneadditional comonomer selected from vinyl acetate, acrylic acid,methacrylic acid. Additional monomers may also form part of thepolymeric structure and these may be selected from esters such as alkylacrylates and the like. A common feature of the non-ethylene monomers isthe presence of a carboxylic acid moiety or precursor to such moiety.Additional acid containing monomers may be selected from diacids such asmaleic or fumaric acid or their anhydrides. The acid containing monomermay comprise up to fifty percent of the polymer. Methods of preparingsuch copolymers are disclosed in, for example, U.S. Pat. Nos. 3,264,272;3,404,134; 3,355,319 and 4,321,337 which are hereby incorporated byreference. Examples of these polymers can be obtained commercially underthe trade names ELVAX® (ethylene vinyl acetate) which is used in avariety of end use applications including as a major component in wiresand cables; NUCREL® (ethylene/methacrylic acid copolymer optionallycontaining an additional softening monomer such as methyl acrylate) andSURLYN® which is a metal ionomer of the above ethylene methacrylic acidcopolymer or terpolymer. Other alkyl acrylates may be selected fromn-butyl acrylate or isobutylacrylate. lonomers are neutralized either inwhole or in part to form metal salts of the acid containing copolymers.These cations are generally selected from metals such as sodium orpotassium or zinc or ther known metal salts or mixtures of these.

Preferred thermoplastic ethylene copolymers are selected from copolymersof ethylene and 2-50%, more preferably 5-25T, by weight of acrylic ormethacrylic acid neutralized up to about 90%, more preferably 5-60% withan alkali metal ion or a divalent or trivalent metal ion, the melt indexof the copolymer being about 0.1-30 or preferably about 0.5-20 dg/min.according to ASTM standard D1238. In addition to selection of thesecopolymers or terpolymers, the present invention may also includeadhesive compositions containing an acid containing polymeric materialsuch as an acid modified (grafted) polymeric material such as EPDM, EPRor other known material which is capable of being acid modified andincorporated into an adhesive composition. As suggested above, since thecopolymers contain an acid containing monomer as a component, residualacid containing monomers may remain in the batch after polymerizationand extrusion or blow molding of film or fabricated parts produced fromsuch copolymeric material. The residual acid may also be a naturaldegradation product of the acid containing ethylene copolymer. Likewise,is adhesives containing an acid modified or anhydride modified ethylenecopolymer such as those sold under the trademark BYNEL® may containtrace amounts of unreacted modifier or may contain decompositionproducts which include acid containing groups. In any case, the finalfilm product or wire and cable or other fabricated part or material oradhesive contains an amount of acid which, absent incorporation of themolecular sieve described below, could affect or harm acid sensitivematerial which comes in contact with the film, fabricated part etc.

The molecular sieve suitable for use in the invention is selected from ahydrophilic sodium aluminosilicate containing less than 5 wt. % ofmagnesium oxide and has a silica/alumina ratio of less than 100 and anominal pore diameter of eight to ten Angstroms. Preferred sieves have asilica/alumina ratio of less than 35 and the most preferred sieves havea ratio of less than 3.0. It is believed that functionality for acidscavenaging can be accomplished with the silica/alumina ratios describedabove. The preferred sieve is generically known as “Type 13X” and issold under the name MOLSIV® 9356. This molecular sieve is typicallyutilized as a surface modifier for polyester film. Other molecularsieves which may also be suitable include products made by UOP soldunder the trademark MOLSIV® 9356 and ABSCENTS® 1000 and 2000 which havesilica/alumina ratios of less than 100. The molecular sieve has anaverage particle size of less than 5 microns. The molecular sieve isutilized and referred to as an “acid scavenger” which also includesadsorption of residual monomeric alkyl acrylates from the ethylenecopolymers or terpolymers which form the other primary component of thecomposition.

The term “hydrophilic” is defined as those molecular sieves which absorbgreater than 10% water at 25° C. and 4.6 Torr pressure.

The thermoplastic composition containing both the ethylene copolymersand the molecular sieve is generally prepared by mixing or blending(compounding) the components before extrusion or formation of a film,adhesive or fabricated part. The amount of molecular sieve added to theethylene copolymer resin depends upon the particular acid content of theethylene copolymer as well as the acid sensitivity of the product whichis to be packaged or exposed to the packaging material made from thethermoplastic composition. Typically the sieve will comprise at least0.5% by weight of the composition, more typically 0.5-2.0% by weight ofthe final film or end product and can also be made as a concentratewhich is diluted with pure resin as needed. The ratios in this lattercase will vary considerably. The amount of sieve in the finalcomposition may also be as low as 0.1 wt. % if some acid removal isrequired.

In addition to the above-mentioned composition components, thecomposition or materials made therefrom may further include otheradditional components including polymeric components as well asingredients or additives conventionally employed in the art for variouspurposes in polymer compositions, such as dyes, pigments, fillers,antioxidants, fire-retarding agents etc. When such optional excipientsare included, they are present in a weight percentage or loading levelthat is typical for that particular excipient.

Films, adhesives, wire and cable elements or other fabricated partscontaining the above thermoplastic compositions are prepared accordingto conventional means such as extrusion, blow molding, cast filmprocessing or injection molding. Peelable seal layers as packagingmaterial may be formed from the thermoplastic composition and used topackage or wrap acid sensitive materials such as surgical sutures. Filmlayers made from the compositions of the invention may be utilized asthe internal layer of a multilayer structure which is utilized to wrapor package acid sensitive material. Absorption of the acid or acidmaterial internally (from within the polymer in the form of acomposition as claimed herein) prior to its use as a packaging materialis superior to placement of an acid-scavenging coupon within the packagealong with the acid sensitive material. In the latter case, acidicvapors from an untreated polymer can migrate into the headspace of thepackage and contact the acid sensitive product prior to absorption bythe coupon. A similar situation occurs when it is desired to absorbunpolymerized monomer from the polymer prior to its use as a packagingmaterial.

In the case of ethylene/vinyl acetate wire and cable insulation, theprocess of vulcanizing a semiconductive composition made from thispolymer usually is carried out at a temperature at which the polymer isnot very stable. The instability is evidenced by liberation of aceticacid that can cause corrision of the metallic conductor and thus,premature failure. Incorporation of the acid-scavenging agent preventsthe acetic acid from contacting the conductor and therefore contributesto maintaining maximum use life.

EXAMPLES

Below are examples of the use of a powdered hydrophilic zeolite toremove low molecular-weight organic materials from ethylene copolymerresins, especially acids such as acetic and methacrylic acids, andmonomers such as isobutyl acrylate. The removal capability of thezeolite is important in certain end-use applications where the presenceof these organic materials are detrimental. Examples of such end usesare in the packaging of certain medical diagnostic test kits, where theacids interfere with the test chemicals and cause incorrect results; inthe packaging of acid-sensitive materials such as absorbable surgicalsutures and implantable medical devices such as screws that are madefrom lactide polymers, where acidic materials from the packagingtransferred in the vapor phase causes premature loss of physicalproperties of the packaged product; in the compounding, extrusion,curing, and end-use of wire insulation compounds made from EVA resins,where the thermal degradation of the EVA resin causes liberation ofwire-corroding acetic acid; and in the removal of residual acrylatemonomer from polymers containing these monomers for organoleptic reasonsfor food packaging.

Example 1

Earlier work had shown that hydrophobic zeolites added to an ionomerresin did not completely remove undesired acetic acid. For instance, inheadspace testing of packages made from aluminum foil coated with a zincionomer, it was found that unmodified ionomer gave 335 ng/package ofacetic acid. Addition of 0.5 wt. % of hydrophobic zeolite reduced theacetic acid level to 334 ng, and addition of 2.0 wt. % reduced the levelto 188 ng.

Screening experiments were carried out to test the efficacy of differentpowdered hydrophilic zeolites for removal of acetic acid. The typesscreened are known generically as types 4A, 5A, and 13X. An initialscreening showed that type 4A zeolite had a lower total sorptioncapacity than the other two. More detailed comparisons were carried outon types 5A and 13X. All of these tests employed headspace gaschromatography, to analyze and quantify the components in the vaporspace above a sample. 25 In these experiments, 18-19 milligrams (mg) ofthe selected zeolite sample was placed in a headspace sample vial thatwas sealed with a cap having a rubber septum. A solution was made up ina 25 ml volumetric flask containing 12.54 g of water and 13.90 g ofacetic acid. Following mixing, either 1, 3, or 5 microliters (μl) ofsolution were injected into a vial containing the test zeolite, aprocess called “spiking”. The headspace above the sample was thenanalyzed on the same day as the day of spiking (Day 1), or on the dayfollowing (Day 2).

Table 1 shows the results of these analyses. Examination of the Day 1data for the samples shows that the capacity of type 13X zeolite for thecombination of water and acetic acid is greater than that of type 5A.More importantly, the type 13X zeolite shows on Day 1 a higher capacityfor sorption of acetic acid, although type 5A shows a higher capacityfor sorption of water. These data are confirmed more dramatically on Day2, showing a shift in the equilibrium sorption of the two sorbates. Type13X is seen to absorb less water than on Day 1, but the absorption ofacetic acid increases from 56% to 100% at the highest 5 μl spikinglevel. The absorption of both water and acetic acid by the type 5Asample is increased on Day 2, but at the highest spiking level of 5 μl,the acetic acid removal is only 17% compared to 100% for the type 13Xsample. These data show that type 13X is superior to type 5A in removingundesirable acetic acid. The preferential absorption of acetic acid vs.water for type 13X zeolite was also unexpected.

Example 2

Commercial type 13X zeolite powder having an average particle size ofless than 5 microns (u) was compounded with three different carrierresins to make concentrates containing 20 wt. % zeolite. The carrierresins were: (1) EMAA copolymer containing 9 wt. % MAA (E=ethylene;MAA=methacrylic acid) and having a melt flow index of 10; (2) EMAAcopolymer containing 4 wt. % MAA and having a melt flow index of 11; (3)EVA copolymer containing 32 wt. % VA and having a melt flow index of 43.

The resin and zeolite were added to the hopper of a 30 mm co-rotatingtwin-screw extruder using gravimetric feeders to form a pre-extrudedcomposition of the invention. A nitrogen blanket was used on theextruder hopper. The extruder screws were set up with a moderate mixingprofile. The zone temperatures of the extruder were set, from rear tofront, at 130, 150, 190, 30 and 195° C. The single-hole extrusion diewas also set at 195° C. The strand of molten compound exiting the diewas cooled in a water bath. The excess water was stripped from thestrand using air knives, and then the strand was passed into a strandpelletizer. The cut pellets were collected in a container equipped witha sparge tube that allowed dry nitrogen to be passed through the bed ofcollected pellets. Melt flow index analyses of the products gave valuesof 5.5, 4.3, and 21.3 9/10 min for the above carrier resins,respectively. Ash analyses gave values of 19.6, 20.2, and 21.4 wt. %zeolite in the product concentrates, respectively.

To determine the acid-removal efficacy of the concentrate made withcarrier resin (1), above, comparison extruded sheet was made from a 5MFI zinc ionomer resin known to contain a high level of acidicvolatiles. Sheet was extruded without and with added concentrate. A 1.5in. single-screw extruder equipped with a mixing screw was set at thefollowing barrel temperature profile, from rear to front: 132, 149, 190and 199° C. An attached 8-in. wide sheet die was also set at 199° C. Asample of the ionomer resin was taken from its shipping container andextruded into sheet of approximately 4 mils thickness at a melttemperature of 1 88° C. The extruded sheet was quenched on a chill rolland immediately packaged in hermetically-sealed barrier packaging.

Following extrusion of the above control resin, an extrusion was carriedout with a blend of 90 wt. % of the control resin and 10 wt. % of theconcentrate made from the carrier resin (1), above. The final blendwould contain approximately 2 wt. % of the hydrophilic zeolite. The dryblend of the pellets were placed in the extruder hopper and extruded ina manner identical to that of the control. While extrudate from thecontrol was clear, the melt from the blend was cloudy, showing thepresence of the zeolite. This product sheet was also packagedhermetically in barrier bags.

Multiple extraction headspace gas chromatography was used to quantifyvolatiles from the control sheet, particularly for acetic andmethacrylic acids. In this technique, a sample of the sheet is placed ina headspace sample vial equipped with a rubber septum. The samples werethen heated at 150° C. for extraction times of 60 min. A three-pointextraction gave values of 420 parts-per-million (ppm) of acetic acid and150 ppm of methacrylic acid.

The control sheet and the sheet containing 2 wt. % zeolite was alsotested using conventional headspace gas chromatography at a 60° C.extraction temperature. Different zeolite-containing sheets were heatedfor 30, 60, or 120 min. While the control sheet gave a chromatogramshowing the peaks of acetic and methacrylic acids plus those of otherunidentified compounds, the zeolite-containing sheets showed neither ofthese acids in the vapor space above the samples.

One peak for an unidentified material appeared in the chromatograms forsamples heated for 30 and 60 min. This peak was no longer observed atthe 120 min. heating time.

This example demonstrates the acid scavenging effect of the compositioncontaining the hydrophilic zeolite of the invention.

Example 3

Another concentrate of the type described in Example (2), Type (1),having a carrier resin of a 9 wt. % MAA-content EMAA copolymer, 10 MFIor a carrier resin of 12 wt. % MAA-content EMAA copolymer, 14 MFI, wascompounded with 30 wt. % of the same type 13X zeolite. A twin-screwextruder was also employed for making this compound in much the samemanner as employed in Example 2. A peelable seal composition wascompounded using 7 wt. % of this concentrate, 71.2 wt. % of anethylene/methacrylic acid (15%) zinc ionomer (neutralized withapproximately 20% zinc), 17.8 wt. % of a commercial butylene-ethylenecopolymer blended with polypropylene made by Shell Chemical, and 4 wt. %of a concentrate of an EMAA copolymer containing 1.0 wt. % of a hinderedphenol antioxidant made by Ciba-Geigy. The same twin-screw extruder usedto make the zeolite concentrate was used to prepare the peelable sealcomposition. This peelable seal composition was coextrusion coated witha tie layer onto the aluminum surface of a composite film made of aprimed oriented polyester resin film extrusion laminated to aluminumfoil with LDPE. The tie layer was in contact with the aluminum surfaceto form the multilayer structure wherein the innermost layer would bethe peelable seal composition layer in a package made from thismaterial. The LDPE layer was in between the primed polyester layer andthe aluminum layer.

The tie layer resin was made with 7 wt. % of the zeolite concentrate, 4wt. % of the antioxidant concentrate, and 89 wt. % of a 9 wt. % MAA,EMAA resin. This resin was also melt compounded with the twin-screwextruder and pelletized. Headspace gas chromatographic testing ofpellets of this tie layer resin without zeolite showed the presence ofboth acetic and methacrylic acids as shown by their peaks in the gaschromatogram. Testing of the compounded tie layer pellets that containedzeolite and antioxidant showed that the acetic and methacrylic acids hadbeen removed from the resin, as shown by the disappearance of the peaksfor these materials in the chromatogram.

Another oriented polyester/aluminum foil composite web was coated usinga pre-compounded 5 MFI zinc ionomer selected from anethylene/methacrylic acid (9%) zinc ionomer resin (neutralized withapproximately 20% zinc) containing 7 wt. % of the zeolite concentrate.This web was then sealed to the web described in the previous paragraphhaving the peelable seal coextrusion coating. The heat sealer, equippedwith 1″ wide sealing bars, was set at 60 psi air pressure and a jawclosure dwell time of 2 sec. Seals which peeled at a force of 3 to 4lb/in width were obtained at bar temperatures ranging from 105 to 170°C. Failure of the seals was at the interface of the sealing layers. Thesurface of the peeled samples exhibited “blushing” or whitening of thepeeled surfaces. This example demonstrates that there was a very goodheat seal between the innermost layer of the oriented polyester/aluminumfoil composite web (multilayer structure having the peelable sealcomposition) and the web described above and is thus useful as apeelable material in those end uses that require this kind ofperformance (e.g. like suture packages and the like).

Example 4

A concentrate containing 30 wt. % of the type 13X zeolite used in priorexamples was compounded with 0.5 wt. % of hindered phenol antioxidant inthe 9 wt. % MAA-content EMAA copolymer, 10 MFI. A Banbury was used tocompound these ingredients. At the end of the blending cycle, theproduct was discharged and transferred into an extruder that fed anunderwater pelletizer. The melt-cut pellets were dewatered, screened toremove fines and agglomerates, dried, and packaged.

The pellets from this production were tested for efficacy in sorption ofacetic acid. Headspace gas chromatography was used, and the acetic acidwas not directly placed on the pellets, but transferred in the vaporphase. The pellet samples and various quantities of acetic acid wereheld at 60° C. for these tests. At the 1 wt. % acetic acid additionlevel, 100% removal was obtained within a 24 hr. holding period. At the2 wt. % addition level, 99.9% removal was obtained after 24 hrs., and by4 days the removal was 100%. At the 3 wt. % addition level, 99.9%removal was obtained in 24 hrs., and 100% within 4 days.

Example 5

A peelable seal layer composition similar to that of Example 3 wascompounded using the zeolite concentrate of Example 4. The followingresins were compounded in a twin-screw extruder and pelletized: 10 wt. %of the zeolite concentrate of Example 4; 65 wt. % of the zinc ionomer ofexample 3 having an MFI of 14; and 25 wt. % of the same blend ofpolypropylene with butylene-ethylene copolymer of Example 3. In a mannersimilar to that of Example 3, the resin was coextrusion coated onto thefoil side of a composite film of oriented polyester laminated to foil. Atie layer of 9 wt. % MAA-content EMAA resin containing 10 wt. % of thezeolite concentrate of Example 4 was used. During the course of coating,several small sheets of unprimed polyester resin (“slipsheet”) wasplaced between the melt and the substrate. Because the melt did not bondto the unprimed polyester, it would allow the coating layers to beisolated at a later time.

A sample of the coated structure containing the slipsheets was removedfrom the coated rollstock and wrapped in aluminum foil so that anyvolatiles from the structure would be contained within the package. Thepackage was transported to the gas chromatographic testing location,where the coating was separated from the slipsheet and the rest of theweb structure. A portion of the coating in film form was placed in aheadspace test vial. Headspace testing as described in Example 3 wascarried out on the isolated film. The testing showed that peaks due toacetic or methacrylic acid were absent.

Example 6

A peelable seal layer composition, (A), intended for sealing liddingmembranes to thermoformed plastic containers was prepared by meltblending the following components: 45 wt. % of an ethylene terpolymercontaining 10 wt. % isobutyl acrylate and 10 wt. % MAA at a MFI of 35;15 wt. % of a hydrogenated hydrocarbon tackifying resin having aring-and-ball softening point of 125° C.; 25 wt. % of a low densitypolyethylene resin having a density of 0.915 and a Ml of 15; 10 wt. % ofa very low-density polyethylene resin having a density of 0.900 and a Mlof 3.5; and 5 wt. % of a concentrate having a carrier resin consistingof a 9 wt. % MAA, EMAA copolymer at a MFI of 10 and containing 11 wt. %of N-oleyl palmitamide and 4 wt. % of behenamide.

A second composition, (B), was made up similar to the above, except thatthe respective percentages of the components were: 40, 15, 23, 10, 5,and additionally, 7 wt. % of the zeolite concentrate of Example 4.

The above compositions were coated onto aluminum foil. At a sealingtemperature of 121 ° C., 40 psi air pressure, and a heat sealing dwelltime of 1 sec., composition (A) sealed to itself gave an average sealstrength of 2.2 lb/in while composition (B) gave an average of 2.1lb/in. At a sealing temperature of 149 ° C., (A) gave an average 3.2lb/in and (B) gave an average 3.1 lb/in. The foil adhesion of coating(A) immediately after coating was 1.3 lb/in, increasing to 1.4 lb/inafter one week. The foil adhesion of coating (B) for these same timeswas 1.6 and 1.9, respectively.

The odor of the two resin pellet samples was compared by a sensorypanel. A rating of 0 indicates the best (lowest) odor, while a rating of8 indicates the worst (highest) odor. Much of the odor is due toresidual unpolymerized isobutyl acrylate in the ethylene terpolymerresin. The human nose can detect very low concentrations of thismaterial. The pellets of (A) were rated 3.2 by the panel, while thepellets of (B) were rated 1.5. These organoleptic scores indicate asubstantial reduction of the odor of the composition containing thezeolite.

Example 7

This example relates to the use of type 13X zeolite for removal ofacetic acid generated in the course of extrusion, vulcanization, and useof EVA semiconductive compounds for electrical cable sheathing.

It is known that EVA resins are sensitive to thermal degradation,liberating acetic acid and forming unsaturation in the polymer backbonewhen the resin is exposed to elevated temperatures. The Material SafetyData Sheet for EVA resins states that the resins should not be exposedto temperatures above 230° C. for short periods of time nor over 204° C.for long periods of time.

For coating of metallic electrical wiring, liberation of acetic acidfrom the insulation is undesirable because of its corrosive effect onthe conductor. Incorporation of the zeolite into the EVA insulationcomposition at a level of less than 1.1 wt. % is able to scavenge morethan 99% of acetic acid liberated at a test temperature of 140° C.Zeolite concentrate as described in Example 2, type (3), was used as aconvenient means of adding zeolite to the composition. A control samplenot containing zeolite was found to liberate 370 μg of acetic acid pergram of compound under the same test conditions.

The above examples are non-limiting and effectively show that anyethylene acid copolymer or ionomer derived therefrom includingterpolymers which has or may develop an acidic or mono alkyl esterresidue can be blended or treated with the 13X molecular sieve toeffectively remove these contaminants. This composition is thereforeparticularly useful in those packaging or fabricated part applicationswhich ultimately contain acid or low pH sensitive material. Of course,this composition can be blended with other polymeric materials whichtogether form the packaging material.

TABLE 1 Sorption of Water and Acetic Acid by Types 13X and 5A MolecularSieves* Water Acetic Acid Spike, μg % Spike, μg % Type μg remain Sorbedμg remain Sorbed Analyses Carried Out the Same Day as Spiking 13X  502 0 100  556   0 100 1500  0 100 1570   0 100 2510 805  68 2780 1230  565A  502  0 100  556   0 100 1500 105  93 1670 1390  17 2510 600  76 27802780  0 Analyses Carried Out the Day After Spiking 13X  502  0 100  556  0 100 1500  23  98 1670   0 100 2510 1600   36 2780   0 100 5A  502  0100  556   0 100 1500  0 100 1670  320  81 2510 160  94 2780 2300  17*Test Methodology

Gas chromatographic headspace vials were filled with 18 to 19 mg of thetest molecular sieve (zeolite) sample. A solution containing 12.54 g ofwater and 13.90 g of acetic acid was made up in a 25 ml volumetricflask. To each vial was added 1, 3, or 5 μl (microliters) of solution.These addition “spikes” gave the paired amounts of water and acetic acidfor each test sample. The vials were then analyzed either on the sameday of spiking, or the following day, to give the results shown. Valuegiven are μg (micrograms) remaining, or the percent of water or acetieacid absorved.

What is claimed is:
 1. A process for removing unwanted acid or monomericacrylate from an ethylene/acid copolymer comprising, i) preparing athermoplastic composition comprising an ethylene/acid copolymer orionomer thereof or an ethylene/acid/acrylate terpolymer or ionomerthereof or an ethylene/vinyl acetate copolymer wherein the compositioncontains residual acid, and ii) adding to the composition an acidscavenging agent selected from a hydrophilic molecular sieve whichcomprises a sodium aluminosilicate containing less than 5 wt. % ofmagnesium oxide and having a silica/alumina ratio of less than 100 andhaving a nominal pore diameter of 8-10 Angstroms.
 2. The processaccording to claim 1 wherein the thermoplastic composition has a meltflow index (MFI) of greater than 0.7 decigrams/min.
 3. The processaccording to claim 1 wherein the ethylene copolymer is selected from anethylene acrylic acid or ethylene methacrylic acid copolymer with anethylene content of at least 50% and the ionomer is selected from co- orterpolymers of ethylene with acrylic or methacrylic acid wherein atleast 5% of the acid groups on the co- or terpolymer are neutralizedwith a mono-or divalent metal ion and the ethylene content is at least60 wt. %.
 4. The process according to claim 3 wherein the metal ion isselected from zinc or sodium and the amount of neutralization with saidmetal is from 10 to 60%, wherein the acid content of the ionomer rangesfrom 4 to 35 wt. %, and an optional termonomer, if present, is selectedfrom alkyl acrylates or methacrylates or vinyl acetate, in a wt. % rangeof 1-30 wherein the ethylene content of the ionomer is at least 60 wt.%.
 5. The process according to claim 1 wherein the molecular sievepreferentially absorbs acetic acid over water.
 6. The process accordingto claim 1 wherein the silica/alumina ratio is less than
 35. 7. Theprocess according to claim 6 wherein the silica/alumina ratio is lessthan 3.0.
 8. A method for packaging or containing an acid sensitivematerial comprising, i) preparing a film or material comprising athermoplastic composition comprising an ethylene/acid copolymer orionomer thereof or an ethylene/acid/acrylate terpolymer or ionomerthereof or an ethylene/vinyl acetate copolymer and an acid scavengingagent selected from a hydrophilic molecular sieve which comprises asodium aluminosilicate containing less than 5 wt. % of magnesium oxideand having a silica/alumina ratio of less than 100 and having a nominalpore diameter of 8-10 Angstroms and ii) packaging the acid sensitivematerial with said film or material.
 9. The method according to claim 8wherein the ionomer is selected from a co- or terpolymer of ethylenewith acrylic acid or methacrylic acid, wherein at least 5% of the acidgroups on the ionomer are neutralized with a mono- or divalent metal ionand the ethylene content is at least 60 wt. %.
 10. The method accordingto claim 8 wherein the acid sensitive material is a suture.
 11. Athermoplastic composition comprising, an ethylene/acid copolymer orionomer thereof or an ethylene/acid/acrylate terpolymer or ionomerthereof or an ethylene/vinyl acetate copolymer and, an acid scavengingagent selected from a hydrophilic molecular sieve which comprises asodium aluminosilicate containing less than 5 wt. % of magnesium oxideand having a silica/alumina ratio of less than 100 and having a nominalpore diameter of 8-10 Angstroms.
 12. A composition according to claim 11wherein the silica/alumina ratio is less than
 35. 13. A compositionaccording to claim 11 wherein the molecular sieve is present in a wt. %relative to the total composition of0.1-30%.
 14. A composition accordingto claim 11 having an MFI of between 1 and 30 decigrams/min.
 15. Acomposition according to claim 11 wherein the molecular sievepreferentially absorbs acetic acid over water upon exposure of saidcomposition to an aqueous/acetic acid environment.
 16. A peelable sealcomposition, comprising (a) an ethylene/acid copolymer or ionomerthereof or an ethylene/acid/acrylate terpolymer or ionomer thereof or anethylene/vinyl acetate copolymer and, an acid scavenging agent selectedfrom a hydrophilic molecular sieve which comprises a sodiumaluminosilicate containing less than 5 wt. % of magnesium oxide andhaving a silica/alumina ratio of less than 100 and having a nominal porediameter of 8-10 Angstroms; and (b) a mixture of (i) a polyolefin resinselected from a homopolymer or copolymer of polybutylene or blends ofsaid polymers with a polypropylene; or a homopolymer or copolymer ofpolypropylene and (ii) an ethylene acid copolymer or ionomer thereof.17. A multilayer packaging structure comprising, (a) an innermost layercomprising a thermoplastic ethylene copolymeric composition comprisingan ethylene acid copolymer or terpolymer of ionomer thereof and azeolite selected from a molecular sieve which comprises a sodiumaluminosilicate containing less than 5 wt. % of magnesium oxide andhaving a silica/alumina ratio of less than 100 and having a nominal porediameter of 8-10 Angstroms; and (b) at least one additional polymeric ormetallic or non-metallic layer.
 18. The multilayer structure accordingto claim 17 wherein the additional polymeric layer may be selected froma thermoplastic ethylene copolymeric composition comprising an ethyleneacid copolymer or terpolymer or ionomer thereof and a zeolite selectedfrom a molecular sieve which comprises a sodium aluminosilicatecontaining less than 5 wt. % of magnesium oxide and having asilica/alumina ratio of less than 35 or may be selected from a layercontaining an ethylene copolymeric packaging material which is anethylene/acid copolymer or ionomer containing film which does not havethe molecular sieve contained therein or other polymeric material suchas polyester and the metal layer may be selected from aluminum.